Improve Streaming's Server Sent Events code

[ThisIsMissEm]

Pitch

Currently in the streaming server we have a custom Server Sent Events code, which is a little brittle and doesn't give a unified API between our websocket usage and SSE, this complicates a bunch of the downstream code.

Motivation

This resolves some tech debt in the streaming server.

[ThisIsMissEm]

One option I looked at was using (Hono's SSE)[https://github.com/honojs/hono/blob/main/src/helper/streaming/index.ts] module or HyperExpress's SSE code

Tonight I've come across better-sse which looks really good, and may be better that the other options I'd found. We'd still likely want a small shim to give a consistent API regardless of transport mechanism.